Huge thanks to the msysgit team for their hard work, because after some testing I've discovered that their git/git-svn port does work, whereas trying to get it working under Cygwin is a quite broken right now. Got git it!

Note: You need to get the Git-1.5.5-preview20080413.exe release if you want to try git-svn, the Git-1.5.6.1-preview20080701.exe release has a broken git-svn.